Advanced Biomaterials Chemistry, Faculty of Forestry, University of British Columbia, Vancouver, BC V6T 1Z4 Canada.
Biomacromolecules. 2010 Apr 12;11(4):1074-81. doi: 10.1021/bm100034t.
The effect of hydrophilic and hydrophobic interactions on the rheological and microstructural behavior of cellulose acetate (CA) in a ternary CA, N,N-dimethylacetamide (DMA), nonsolvent (alcohol) system was examined. Increasing nonsolvent concentration increased the viscosity and dynamic viscoelastic properties of the system. At a critical nonsolvent concentration, a sol-gel transition was observed, which was dependent on nonsolvent structure. Increasing the available hydrogen bonding groups within the nonsolvent led to higher modulus (stronger gels) and a sol-gel transition at lower nonsolvent concentration. Likewise, increasing the alkyl chain length (hydrophobicity) of the nonsolvent also enhanced the viscoelastic properties; however, hydrogen bonding, specifically the ability to hydrogen bond donate was critical for gel formation. For all gels studied, the elastic modulus shifts to higher values with increasing hydrophilicity and hydrophobicity of the nonsolvent and exhibits a power-law behavior with nonsolvent content. All of the gels exhibit similar fractal dimensions; however, confocal images of the different systems reveal distinct differences. Increasing the hydrophilicity of the nonsolvent led to a more uniform denser gel microstructure, whereas increasing the hydrophobicity resulted in a larger more heterogeneous network structure despite the increase in moduli.
考察了亲水性和疏水性相互作用对醋酸纤维素（CA）在三元 CA、N，N-二甲基乙酰胺（DMA）、非溶剂（醇）体系中的流变和微观结构行为的影响。增加非溶剂浓度会增加体系的粘度和动态粘弹性能。在临界非溶剂浓度下，观察到溶胶-凝胶转变，这取决于非溶剂的结构。增加非溶剂中可用氢键基团的数量会导致更高的模量（更强的凝胶）和更低的非溶剂浓度下的溶胶-凝胶转变。同样，增加非溶剂的烷基链长度（疏水性）也会增强粘弹性能；然而，氢键，特别是氢键供体的能力对于凝胶形成至关重要。对于所有研究的凝胶，弹性模量随非溶剂亲水性和疏水性的增加而增加，并表现出与非溶剂含量的幂律关系。所有的凝胶都表现出相似的分形维数；然而，不同体系的共焦图像显示出明显的差异。增加非溶剂的亲水性会导致更均匀致密的凝胶微观结构，而增加疏水性会导致更大更不均匀的网络结构，尽管模量增加。
